Comparison of In Vivo Three-Dimensional Glenohumeral Positions and Scapular Kinematics between Young and Older Male Groups

BACKGROUND: Many researchers have questioned whether shoulder kinematics such as the glenohumeral position and scapular kinematics would be different in different age groups. However, studies comparing shoulder kinematics between different age groups have been rare. The aim of this study was to analyze and compare the three-dimensional (3D) glenohumeral position, scapular kinematics, and scapulohumeral rhythm (SHR) during scapular plane arm abduction between a normal young male group and a normal older male group. METHODS: Twenty normal men (10 young and 10 older) were enrolled in this controlled laboratory study. Fluoroscopic images were obtained using a single plane X-ray system. Bilateral computed tomography scans were taken to create a 3D model. A 3D-2D registration technique was used to determine the 3D position and orientation of the bones of the shoulder. RESULTS: During scapular plane arm abduction, there were significant differences in scapular kinematics between the groups. The older male group showed more upward rotation, posterior tilt, and external rotation than the young male group. On the other hand, the glenohumeral position such as superior inferior translation, anterior posterior translation, and external rotation of the humeral head did not show significant difference between the groups. The mean value of SHR for the overall arm elevation range from start to maximum elevation angle for the older group and young group was 2.298 ± 0.964 and 2.622 ± 0.931, respectively, showing a significant difference between the two groups (p = 0.035). CONCLUSIONS: Scapular kinematics and SHR were significantly different between the older male group and the young male group. Our study could provide reference values of shoulder kinematics for older men aged 55–65 years.